A gyro sensor is, for example, used for carrying out a hand-shake correction in a video camera, a video correction in a camera-equipped cellular telephone, or an automobile position control, or the like.
In general, a detection circuit of a gyro sensor outputs an analog detection signal in accordance with the size of an angular rate acting on an oscillator connected the detection circuit, and carries out a calculation on the analog detection signal with a digital calculation device such as a CPU or microcomputer. Therefore, an A/D converter is provided between the detection circuit and the digital calculation device. the detection circuit and the A/D converter, being mounted on separate chips, are each supplied with a reference voltage from separate reference voltage generation circuits.
The conversion accuracy of the A/D converter depends on the reference voltage, and the output reference voltage (the output voltage when at rest) and the angular rate detection sensitivity of the detection circuit depend on the reference voltage. In the event that the power supply voltage fluctuates due to power supply noise or the like, and the reference voltage fluctuates along with it, the full scale voltage of the A/D converter fluctuates, with a bad influence on the conversion accuracy of the A/D converter. Meanwhile, the output reference voltage and the angular rate detection sensitivity of the detection circuit are also affected by a reference voltage fluctuation. As it was the above-mentioned, the detection circuit is connected to the reference voltage generation circuit separate from that of the A/D converter, so there has been a problem in that, not coping with the fluctuation in the conversion accuracy of the A/D converter, the detection accuracy is reduced.
As a way of solving this problem, heretofore, in order to cause a gyro sensor detection signal to depend on the power supply voltage, a gyro sensor with a ratiometric function has been proposed which includes a power supply voltage dependence circuit, which generates a power source dependent correction voltage proportional to the power supply voltage, and a multiplication circuit, which multiplies the power source dependent correction voltage with a detection signal output from a signal processing circuit. And a gyro sensor has been proposed which includes a temperature compensation type ratiometric circuit in order to supply a stable output not only under fluctuation in the power supply voltage but also under fluctuation in temperature.
However, as the heretofore known gyro sensor with a ratiometric function has a complex and a large circuit configuration, it has a drawback in that it cannot comply with the miniaturization of apparatus demanded in recent years.